Stickies and tackies continue to be a problem in secondary fiber pulp and paper mills. It is believed that the problems caused by the build up of stickies and tackies on pulp and papermaking machinery and in the final paper cost the pulp and paper industry many millions of dollars per year in lost production. The terms "stickies" and "tackies", as used herein, are interchangeable terms that primarily include synthetic contraries found in secondary fiber. More particularly, stickies are defined as adherent deposits caused by organic materials used in paper and board coating and converting operations which are typically introduced into paper machine furnishes with recycled fibers. The word "stickies" is derived from the fact that the resultant deposits stick to wires, felts, and other parts of paper machines. Stickies also trap inorganic components found in papermaking furnishes. Stickies are a diverse mixture of synthetic materials ranging from hot-melt and pressure-sensitive adhesives to binders and coatings for inks or wet strength resins. ink residuals, tars and latexes. Polymeric examples include, for example, polyethylenes, polybutadiene-styrenes, polyvinylacetates and polyacrylates.
Stickies are found in secondary fiber and in systems where paper produced in a mill is used as broke. As such, stickies and tackies are distinct from pitch, which is defined as any resin-based deposit of widely varying constituency; pitch is material comprising naturally occurring resinous materials and gums liberated during the screening, heating and refining processes that occur during papermaking. Pitch originates in the extractive fraction of wood. The extractive fraction of wood is a complex mixture of substances which are soluble in water, alcohol, benzene, ether, and/or acetone. The extractive fraction, which generally makes up from about 3% to 10% of the weight of wood, contains such components as low molecular weight carbohydrates, terpenes, aromatic and aliphatic acids, alcohols, tannins, color substances, proteins, lignins, and alkaloids. The constituents of pitch are naturally occurring, as opposed to the synthetic compounds that comprise stickies. While pitch and stickies cause similar problems in papermaking operations, they are distinct both in terms of their origin and their composition. While the present invention is generally directed to stickies control, it will be understood that any pitch present in the paper stream being treated may also be controlled according to the present invention.
Stickies and tackies are a major problem in secondary fiber pulp and papermaking operations because they (1) agglomerate and also occlude other matter to form visible "dirt" in the final paper, (2) plate out and collect on machinery used in pulping and papermaking process such as screens, filters, refining equipment, pulp washers, and paper machines, and (3) reduce pulp brightness and brightness stability. The composition and amount of stickies deposited on pulping and papermaking machinery and in the final paper varies with the type of secondary fiber used in the pulping operation. As used herein, the term "secondary fiber" includes any paper fiber used for a second time in the production of a paper end-product.
Sources of secondary fiber include, but are not limited to, tissue, fine paper, boxboard, linerboard, foodboard and newsprint. Each of these sources generally contains unique impurities, such as inks, colors, fillers, strength resins and/or coatings, which means that the stickies composition and concentration can vary widely from one secondary fiber to another.
The presence of calcium carbonate in the pulping process generally exacerbates the problem of stickies deposition on pulp and papermaking machinery. Crystallized calcium carbonate can provide nucleation sites for precipitated metal soaps thereby producing hydrophobic particles which coalesce with other particles to form a stickies deposit.
There have been many attempts over the years to eliminate stickies problems by adding control agents to secondary fiber pulping and/or papermaking processes. While more thorough deinking and pulp washing operations may help to reduce stickies problems, the most common methods of treatment involve the addition of dispersants or adsorbent fillers to the furnish. For example, treatments may involve the use of zirconium compounds, alum, talc, anionic stickies-control agents such as polynaphthalene sulfonates or modified lignosulfonates, cationic control agents such as polyquaternary ammonium polymers, methylcellulose derivatives and nonionic surfactants. None of these treatments are believed to be particularly effective for stickies control.
U.S. Pat. No. 5,223,097 reports a method for controlling pitch in an aqueous papermaking system by adding to the system a polymer derived from epichlorohydrin, diepoxide, or precursors thereof, and alkyl amine and an amine. Mannich-derivatized compounds do not appear to be disclosed.
Examples of attempts to control pitch with other types of compounds or processes are found in, for example, U.S. Pat. Nos. 3,583,461; 3,703,563; 3,812,055; 3,895,164; 3,896,046; 3,992,249; and 4,313,790.
Zirconium chemicals have also been used to control pitch and stickies. See, for example, U.S. Pat. No. 4,950,361.
The use of melamine formaldehyde-type polymers to control stickies deposition in papermaking is reported in U.S. Pat. No. 5,433,824, and the use of such compounds in the control of pitch deposition is reported in U.S. Pat. No. 5,286,347.
Methods for inhibiting sticky deposition are reported in U.S. Pat. No. 4,995,944, which uses a solution containing a cationic polymer containing a cationic surfactant.
Mannich derivatized phenolic and polyphenolic compounds are described in the art. None of the polyphenolic compounds have been prepared by reaction with an amino acid or other amphoteric compound such as those disclosed herein. For example, U.S. Pat. No. 3,494,889 discloses epichlorohydrin resins that have been cured with Mannich derivatized bisphenol products. The patent teaches a bisphenol product having four Mannich substitutions of the formula CH.sub.2 NHR, where R is hydrogen, methyl, ethyl, N-propyl, N-butyl, or alkenyl of three to four carbon atoms. U.S. Pat. No. 4,952,732 relates to Mannich condensates of a substituted phenol and alkylamine containing internal alkoxy groups. The invention is reported as relating to Mannich condensates prepared by reacting formaldehyde with phenol or a phenol substituted in the ortho or para position with a hydrocarbon group and also with an alkylamine, where the alkyl group is separated from the amine group by one or more propoxy groups or by a mixture of ethoxy groups and propoxy groups. WO95/28449 discloses a polymer that is a Mannich derivative of a novolac resin. U.S. Pat. No. 4,883,826 discloses a polyol prepared by alkoxylating a Mannich condensate of a phenolic compound, formaldehyde, and a mixture of diethanolamine and at least one other alkylamine. U.S. Pat. No. 4,917,729 discloses metal chelating compounds that are Mannich derivatized bisphenol compounds, having two Mannich groups, one attached to each ring of the bisphenol A. U.S. Pat. Nos. 4,795,505 and 4,792,355 relate to a similar compound having only a single phenol ring and a single Mannich substituent. There is no disclosure of the use of amino acids or other amphoteric compounds in the Mannich Reaction in any of these references. Nor is there any disclosure of use of a di- or polyphenolic Mannich derivative to reduce stickies in paper treatment.
Chem. Abstract 83:10779 reports a Mannich reaction of glycine and formaldehyde with substituted phenols. Only single aromatic ring phenols are reported and the abstract is silent as to the derivitization of polymers. Similarly, no use of the compounds is disclosed.
None of the above patents teach compositions that have at least two aromatic rings that have been Mannich-derivatized using an aldehyde and an amphoteric compound having both an amine and acidic moiety. Nor do any of the references teach the use of such compounds, or any related compounds in the reduction of stickie formation. There remains a very real and substantial need, therefore, for compounds useful in such applications.